1. Field of the Invention
The present invention is in the field of wastewater treatment, particularly water containing harmful organic contaminants. The invention is a small part of a large and complex reactor that is used for purifying contaminated water. As the reactor purifies the water, there is a tendency for reaction products to be deposited on the internal walls and tubing of the reactor, thereby reducing the efficiency of the process. The present invention is used to remove the unwanted deposits from the interior of the reactor so as to maintain its efficiency.
2. The Prior Art
In U.S. Pat. No. 4,897,246 issued Jan. 30, 1990, there is described a type of oxidation chamber in which a liquid contaminated by undesirable organic compounds is treated. As the liquid passes through the oxidation chamber, it is subjected to intense ultraviolet radiation from powerful ultraviolet lamps that are mounted inside quartz tubes that extend through the liquid in the reaction chamber. Simultaneously, the liquid is subjected to chemical attack by the injection of hydrogen peroxide and possibly other reagents. Complex chemical reactions take place within the reactor because typically a number of contaminants are present simultaneously. U.S. Pat. No. 4,897,246 has been assigned by the present inventor to a predecessor of the assignee of the present invention.
One of the problems encountered in using the reactor was the fouling of the quartz tubes by reaction products. The fouling reduced the optical efficiency of the chamber to a point where it became necessary to interrupt the process and to remove the quartz tubes for cleaning.
In an attempt to overcome the need for interrupting the process, a shuttling scraper was developed. The shuttling scraper encircled a quartz tube and was pushed through the chamber by the pressure and flow of the liquid being treated. Upon reaching the end of the quartz tube, the scraper would park itself unobtrusively and await an occasional reversal in the direction of flow which would then carry the shuttling scraper to the opposite end of the quartz tube. The shuttling scraper and a hydraulic system for reversing the flow are described in greater detail in U.S. Pat. No. 5,227,140. The disclosures of U.S. Pat. Nos. 4,897,246 and 5,227,140 are incorporated by reference into the present description.
FIG. 1 is adapted from U.S. Pat. No. 5,527,140 and shows a shuttling scraper 12 of the prior art moving from left to right in FIG. 1 within a tubular reaction chamber 14. The shuttling scraper wipes the inside surface of the tubular reaction chamber 14 and simultaneously wipes the outside surface 16 of the quartz tube that encloses an ultraviolet lamp. After having traveled the length of the tubular reaction chamber 14, the shuttling scraper parks within an end manifold 18 while awaiting a reversal in the direction of flow of the liquid within the reactor.
The structure of the shuttling scraper of the prior art, shown enlarged in FIG. 2, is surprisingly simple. It includes a first wiper assembly 20, a second wiper assembly 22, and a spring 24 interconnecting the first wiper assembly and the second wiper assembly. The first and second wiper assemblies 20 and 22 have identical structures. A wiper 26, having the form of an annular disk and composed of a fluoroelastomer is sandwiched between two washers 28 and 30. The sandwich is held together by screws, of which the screw 32 is typical.
The spring 24 yieldingly resists both compression and tension, and is composed of a stainless steel wire in the preferred embodiment. The spring 24 serves as a resilient spacer to maintain the separation between the wiper assembly 20 and the wiper assembly 22.
The shuttling scraper cleans not only the inside surface of the tubular reaction chamber 14, but also cleans the outside surface of the quartz tube 16. The outside diameter of the wiper 26 is a few thousandths of an inch larger than the inside diameter of the tubular reaction chamber 14 and the inside diameter of the wiper 26 is a few thousandths of an inch less than the outside diameter of the quartz tube 16. In this manner, the wiper 26 engages the inside of the tubular reaction chamber 14 and the outside of the quartz tube 16 in an interference fit. The shuttling scraper is pushed through the tubular reaction chamber 14 by the entire force of the liquid and is not merely urged along by hydrodynamic drag.
Experience has demonstrated the soundness of the design of the shuttling scraper, but out of this experience has grown several ideas, described below, for greatly improving the efficiency of the shuttling scraper, particularly in difficult wiping applications.